Myasthenia gravis (MG) is a disorder of neuromuscular transmission, resulting from binding of autoantibodies to components of the neuromuscular junction, most commonly the acetylcholine receptor (AChR). The main manifestation is easy fatigue of the affected skeletal muscles, which often worsens after activity and improves after rest (“morning lightness and evening heaviness”).
According to the Myasthenia Gravis Foundation of America (MGFA), MG can be classified into types I to V, of which type IIIb mainly involves the pharyngeal muscles and is less commonly encountered in clinical practice.
Case Presentation
The patient was a 62-year-old man who was admitted to the hospital on 25 June 2021, with a complaint of episodes of slurred speech for 20 days that had worsened in the previous 9 days. The main manifestations are slurred speech and slower speech speed.
Medical History
- The patient had a history of hypertension (>20 years), diabetes mellitus (8 years), and coronary heart disease (8 years).
- At the age of 16 years, the patient developed bilateral vision loss after retinal detachment following trauma to both eyes.
- The patient denied habits such as smoking and alcohol consumption.
Family History
- unremarkable
Clinical Exam
Physical examination revealed:
- On admission (at the onset of disease), his temperature was 36.5°C, heart rate was 70 beats per minute, respiratory rate was 17 beats per minute, and blood pressure was 144/86 mmHg.
- Both irises were light greyish-white in colour, with no light perception, irregular bilateral pupils, and loss of direct and indirect light reflexes.
- Dysarthria; tongue extension in the centre; limb muscle strength grade 5; normal muscle tone; negative Babinski sign; and bilateral Chaddock reflex were also identified.
Laboratory examination revealed:
- The initial diagnosis on admission was transient ischemic attack.
- Electromyography tests was positive and negative for the remaining nerves.
- Chest computed tomography revealed a small number of inflammatory, fibrous foci in both lungs but no thymoma.
- Autoantibody profile testing for neuromuscular junction disease revealed an AchR-Ab immunoglobulin-G (IgG) level of >20 nmol/L (<0.45 nmol/L is considered negative).
- Therefore, the clinical diagnosis was MG (type IIIb).
Treatment
Oral administration of pyridostigmine bromide 60 mg three times daily (TID) was started.
Clinical Outcome
A follow-up telephone call 2 months after discharge revealed that the patient had adhered to the 60 mg TID regimen of pyridostigmine bromide without recurring symptoms of slurred speech.